Splachnum paradoxum R. Brown, Chlor. Melvill., 44. 1823; Tetraplodon mnioides var. paradoxus (R. Brown) Jensen

Plants 2-4 cm, light green or yellow-green. Leaves ovate, concave, 2-5 mm; margins entire or nearly so; apex acuminate; costa ending in subula; distal laminal cells hexagonal, 30 µm. Sexual condition autoicous. Seta clear pale yellow to stramineous, 2-3.5 cm. Capsule cleistocarpous, clear pale yellow to stramineous, spindle- or club-shaped; hypophysis conspicuously narrower than urn; stomata confined to distal hypophysis; operculum not developed. Calyptra cucullate or conic-mitrate. Spores 9 µm, smooth.

Capsules mature summer. Caribou or muskox dung; moderate to high elevations; Greenland; N.W.T., Nunavut, Yukon; Alaska; n Europe (Arctic Russia).

Tetraplodon paradoxus is much confused in the literature with T. pallidus (W. C. Steere 1977), although the two are easily distinguished. Tetraplodon paradoxus is cleistocarpous, the setae are longer (to twice as long), leaves smaller and more narrow, and capsules are darker and spindle- or club-shaped, with the hypophysis noticeably narrower than the urn and having fewer stomata. Steere suggested that spore dispersal to fresh dung might occur when the sporophytes are ingested by caribou or muskoxen and the spores subsequently dropped in dung at some other location.